Refrigerating compression cycle



March 26, 1940. p SCI-ILUMBQHM 2,195,388

REFRIGERATING COMPRESSION CYCLE Filed March 28, 1939 '4 ShQQtSyShBBt 1 March 1940. P. SCHLUMBOHM I 533 REFRIGERATI NG COMPRESSION CYCLE Filed March 28, 1939 4 Sheets-Sheet 2 INVENTOR March 26, 1940. sc u 2,195,388

- RBFREIGERATING COMPRESSION CYCLE I Filed March 28 1939 4 Sheets-Sheet 3 INVENTOR.

March 26, 1940. P. SCHLUMBOHM 2,195,383

RBFRIGERATING COMPRESSION CYCLE Filed larch 2a; 1939 4 Sheets-Sheet 4 INVENTOR UNITED sTATEsj PATENT OFFICE momma COMPRESSION-(H013 Application March 28,1939, Serial No. 284,506

11 Claims.

The instant invention relates to a refrigerating system of the type described in my United States Patents Numbers 1,935,749 and 2,082,850. In systems of this type the compressor is'driven by a combustion motor and the fuel for the motor is used as a temporary refrigerant throughout the thermo-dynamic cycle of the compression refrigeration system before being used as fuel in the combustion motor. A predetermined supply of refrigerant, much greater than, normally required in standard closed refrigerating systems, must be provided to make up for the fuel consumption. In my United States Patent No; 1,935,749, it is suggested that the refrigerant supply be stored within the receiver tank associated with the condenser;' and in my United States Patent No. 2,082,850, it is contemplated that portable containers for compressed gases, like propane or butane, be used as the evaporator in the refrigerating system, thereby making the portable containers a functional part of the refrigerating circuit. While these patented constructions and methods are workable, the present invention is an improvement thereover.

In accordance with the invention, the supply of refrigerant-fuel is kept in a storage container connected to the refrigerating system and a re-' frigerant is admitted to the refrigerating system only in a restricted amount which is controlled so with respect to time. Whereas in my aforementioned patents, the whole supply of refrigerant-fuel was admitted at one time to a refrigeratingcycle which may be termed a temporary cycle". The instant invention involves a refrigcrating circuit which is interposed between the storage tank and the combustion motor through which circuit a small portion of the supply is passedfrom tlmetotiineintransitonitsway from the storage tank to the intake of the motor.

40 I term this latter cycle a transitory cycle. One advantage of the transitory cycle is reduction of fire hazard, aswill be better understood from the description which follows. Another distinct advantage of the transitory cycle is its capability of being adapted to the use of such mixtures of hy-' vdrocarbons as constitute the commercial grade of compressed gases such as propane or butane or the like. These commercial mixtures contain small percentages of ethane and/or even methane which cannot be condensed to a liquid in a condenser of a compression refrigeration system built for a propane or butane cycle. In the instant invention, the purging action caused by steadily bleeding condenser gas into the carburetor of the motor is of the greatest importance for it ensures the removal of such non-condensable gases as may be present in the condenser therefrom. While this advantage may be inherent to some 5 extent in the temporary cycle, however, in the transitory cycle the quantity of non-condensable gas introduced into the refrigerating circuit, may

be related to the purging capacity of the motor which may be measured by its fuel consumption. 10

The transitory cycle may be improved by what I term the fast.cycle".- Before applying such relative words like fast or slow, a standard should be chosen with which these words can be compared. I propose to choose as a standard, a 15 compression refrigeration cycle in which the circulating refrigerant cycles once per minute; and I term a cycle in which the refrigerant cycles more than once per minute, a fast cycle. The utilization of the fact cycle does not only greatly reduce the fire hazard because of the very small quantity of refrigerant actually circulating within the refrigerating circuit, but it is also of great practical advantage in .the starting of the operation of the new refrigerating system in accordance with the B5 invention.

Other objects and the nature and advantages of the invention will be apparent from the following description taken in conjunction with the accompanying drawings, wherein: 80

Fig. 1 is a diagrammatic showing of a system involving the transitory cycle and the fast cycle;

Fig. 2 is a diagrammatic view in perspective of a refrigerating system in accordance with the invention, indicating the location of the parts in 86 relation to the insulating wall of the cooling space and showing the mechanical connection between the motive equipment and the refrigerating apparatus;

Figs. 3, 4 and 5 are views partly in section and 40 partly in elevation of one form of the invention which has been actually built and which shows the relation between a packaged refrigeration unit and the wall of the cooling space which it is to cool 1 46 Fig. 6 is a diagrammatic illustration of the electric wiring of a push button starting arrangement;

Figs. 7 and 8 are perspective and elevational views respectively, with parts shown ln-section of 50 a refrigeration unit in accordance with the invention specifically showing the relation between the refrigerating unit and the space to be cooled.

The reference numerals in Figs. 1 to 6 refer to identical or analogous parts as follows:

1 Motor 2 Battery 3 Generator-starter 4 Shaft 5 Condenser blower 6 Evaporator blower 7 Compressor 8 Condenser 9 Evaporator 10 Main thermal expansion valve ll Main constant pres- 12 Evaporator expansion sure valve line 13 Suction line 14 Thermal bulb of l0 15 Pressure line 16 Highest header 1'? Middle header 18 Lower header 1%) Pipe to receiver 20 Receiver tank 21 Pressure equalizer 22 Elbow 23 Feeding line 24 Level take-off 25 Spray 26 Thermal bulb for 29 27 Casing for 26 28 Capillary for 26 29 Bottle feed control 30 Fuel take-oil 31 Pressure reduction 32 Solenoid shut-off 33 Carburetor 34 Airintake of 33 35 Solenoid shut-off 36 Constant pressure valve 37 Strainer 38 Hand valve 39 Flexible hose 40 POL bore 41 Check valve 42 Fuse plug 3 Propane tank 44 Fill-up line 45 Level window 46 Battle 4'7 Baffle 48 Strainer 49 Evaporator blower 50 Condenser blower exhaust exhaust 51 Insulating wall 52 Passage for shaft 4 53 Passage for expan-, 54 Passage for suction sion line L. 13 55 Spark coil 56 Spark coil cable 57 Nozzle 58 Diffuser for 57 59 Switch 60 Starting lever 61 Relays 62-63 Bearings for 4 e4 Solenoid by-pass In Figs. '7 and 8 the reference letters refer to identical or analogous parts as follows:

T Propane tank W Wall of the cooling space Y C Condenser and engine compartment E Evaporator and blower compartment I Insulating wall of the packaged unit.

Referring to Figs. 1 and 2 which illustrate clearly the cycle in accordance with the instant invention, refrigerant enters through line l2 into the evaporator 9. The vapors leave the evaporator through the suction line l3 of the compressor l and pass through the pressure line ii of the compressor into the highest header it of the condenser 8. The condensed liquid flaws through pipe l9 into the receiver tank and elements 20, 22, 20a, and H, and leaves the receiver through pipe 23 which leads to the intake of a thermal expansion valve l0, I4; A pressure valve H is provided between this thermal valve and an evaporator expansion line i2, the importance of which pressure valve l I will be explained later.

The refrigerant circuit thus far described is now interposed between the storage tank 43 and the motor I. In order to simplify the explanation, and by way of example, the refrigerant and the fuel will be referred to as propane, as this chemical compound may be superior to all others for the purposes of this system. However, other fuel gases, like butane, may be used along the new principles of this invention. The connection of the circuit with the motor may be readily efiected and the technical means for such connection is illustrated in Figs. 1 and 2 and comprises the fuel take-of! pipe 30 and the connection of the upper part of the receiver tank with the carburetor 33. On its way through the pipe 30, the fuel gas is heated in a countercurrent heat exchanger utilizing the heat of the compressed gas in the pipe l5 connecting the compressor with the condenser. This arrangement is of importance for it serves to prevent the condensation of propane in the fuel line 30. By means of the pressure reduction valve 3|, the condenser pressure of the fuel gas is reduced to 6 oz. A shut-off solenoid valve 32 serves to close the fuel line in this 6 oz. pressure zone, the moment the motor stops.

The connection between the circuit mentioned and the storage tank 43 is an important consideration. A significant factor involved is the precise control of the flexible line 39 and such control is responsive to the'quantity of propane in the circuit; the line 39 is closed by the control when a predetermined amount of propane is in the circuit and opened if this amount of propane reaches a predetermined minimum by the withdrawal of propane from the circuit through the line 30 so that it may be used as fuel. The control device in accordance with the invention responds quickly and safely to the level of liquid propane in the circuit and effectively shuts off or opens, in accordance with the liquid level, the flexible line 39.

This control device could have been a new structural element but it was found that a satisfactory control device might be effected by applying a standard thermal expansion valve in a new way. In addition to the utilization of the control device, it was essential in accordance with the invention, that the propane refrigerat ing circuit have additional means for regulating the return of flow of propane from the storage tank through line 39.

Further, a safety shut-off valve is provided in line 38 to prevent the propane from leaving the storage tank in case of rupture in the tubing of the refrigerating circuit.

As illustrated in Fig. 1 and Fig. 2, the main control of the flexible line 39 is exercised by the thermal valve 29, which may be of the same type as that of the main expansion valve ID. The pressure of the propane inside the thermal bulb 2B and the capillary 28 isexerted on top of a diaphragm, which exerted pressure is counteracted on the other side of the diaphragm by the pressure of propane in the suction line 13 and also by the force exerted by a'spring which is adjustable. In accordance with this construction and arrangement, when the pressure on the top of the diaphragm is greater than the pressure on the bottom, the valve associated therewith is open. When the thermal bulb 26 is cooled down to the temperature of the evaporator 9, the propane pressures on both sides of the diaphragm become equal and then the force of the spring which is exerted on the bottom side of the diaphragm effects the ,closing of the valve. In accordance with the invention, this correlation of parts in the system is utilized to keep the valve 29 closed as long as a predetermined level of propane is present in the receiver tank 20, and to open the valve 29 automatically when the level of liquid propane has been lowered to a predetermined minimum by fuel consumption. As illustrated in detail in Fig. l, the receiver is specially designed with regard to its structure to effect the formation of a quiet surface of propane at the predetermined minimum level. The receiver is built in the shape of a communicating pipe 2| within which there is located a baiile.

U-shaped pipe 26, 22, and 26a. The upper parts of this U-shaped container are connected by a restriction 46. The reason for this construction is that a greater turbulence within pipe l9 and container 20 prevents the formation of a quiet surface of liquid propane in container 20, which desirable quiet surface may be effected by the utilization of the communicating pipe 20a. The connecting pipe 2| permits the equalization of pressures above the liquid propane of 20 and 20a, and the restriction 46, which consists of a metal disc with a hole in the center, which disc is soldered to the interior walls of pipe 2|, prevents disruption of the quiescent state of the propane liquid by protecting the said liquid from the turbulence of the wet vapor in pipe l9. At a predetermined level, a sight glass 45 is provided.

and a pipe 24 is arranged in the wall of pipe 20a. When the receiver tank 26, 20a is filled with liquid propane up to the level of tube 24, liquid propane will flow through pipe 24, strainer 46 to a nozzle 25 which is directed against the thermal bulb 26. The thermal bulb 26 is mounted within a casing 21 which is connected to the evaporator expansion line l2. The casing 21 serves as an evaporator for a part of the liquid propane which is sprayed against the bulb 26 under the pressure of the condenser and accordingly, the bulb 26 is cooled by. the evaporation of the propane. The remainder of the sprayed propane flows through line 12 into the evaporator and joins propane which has left the constant pressure valve ll. As explained above, the cooling of bulb 26 keeps the valve 29 closed. correspondingly,- when the liquid propane falls below a predetermined level in receiver 20a, there will be no liquid spray available at nozzle 26 to cool bulb 26, and valve 29 will open.

In accordance with the invention, the method of filling the refrigerating circuit from the storage tank involves the passage of propane from the storage tank in a gaseous phase and not in a the storage tank is admitted to the refrigerating.

circuit on the low side and not on the high side. The advantage of this procedure and the construction involved, is that, in connecting the. storage tank with the suction line ll of the compressor, the charging operation becomes independent of the propane pressure in the storage tank 43 for the compressor can pump propane out of the storage tank even if the storage tank is exposed to low atmospheric temperatures and the pressure therewithin is correspondingly low, much lower than the condenser pressure. In addition tothe considerations mentioned, the possibility of high propane pressures in the storage tank must also be considered. In order to build up sufllcient condenser pressure to liquefy valve is so adjusted that it closes if the evaporator pressure exceeds a predetermined maximum which may be 30 lbs. When this pressure is excecded, the valve 29 will open and the storage tank will be connected with the low side.

It being essential to protect the charging operation against excessive storage tank pressures, the intake of the compressor mustbe restricted, as otherwise more propane gas would be pumped into the condenser than the condenser could liquefy, Should the undesired condition described occur, the machine would cease to operate as the condenser would require more work done by the motor than the motor could supply. Accordingly, the flow of propanefrom the storage tank to the low side of the refrigerating circuit I compressor suction pressure which is high enough to efl'ect closing of valve II, but is not much higher. By way of further explanation, when the valve I I has been set to close at an evaporator pressure of 30 lbs., the controls influencing the flow of propane through line 39 will make for a suction pressure in pipe II of approximately 45 lbs. An inexpensive way to provide a restriction in line 39 is to bore a hole 46 through the metal cone of a POL connection such as is used for attaching the flexible hose 39 to the hand valve 38. In a one-ton unit, a hole 46 with a diameter of approximately one-sixteenth of an inch will serve this purpose. However, in order to provide a margin of safety against the influence of wide fluctuation of pressure in tank'42,;the constant pressure valve 36 may be preferred. This valve 36 may be set for a maximum pressure in the low side of approximately 45 lbs. The safety device mentioned above may take the form of the solenoid shut-off valve 35. The apparatus further includes the strainer 31 and valve 38, check hazard associated with the use of propane in its application as a refrigerant, as surprisingly small amounts of propane are suflicient to effect the refrigerating cycle. In addition to the theoretical quantity of liquid refrigerant that is required as a minimum to provide the required heat exchange by wetting the interior walls of the evaporator, which requires very little liquid if the "dry-feeding" method is applied with the aid of a thermal valve l6, only small additional quantitles of liquid propane are necwsary to make up for the time lag between the evaporation and the arrival of condensate to the receiver 26. In accordance with the invention, it is possible to operate a-one-ton unit with as little as a pint of propane (a pint of propane weighs about half a pound and one gallon of propane is the equivalent of 4.25 lbs.) and this small quantity is apparently not the practical minimum. Under standard conditions (evaporator at 5 and condenser at the weight of propane circulated per minute per ton of refrigeration is 1.646 lbs. thus,

operating the cycle with half a pound of propane means that the propane cycles about three times per minute in what has been termed a fast cycle.

In order to eliminate fire hazards resulting 7 from leakage in thetubing and connections in the refrigerating system, a special method has been provided to detect such leakages. The apparatus required for this method is shown in Fig. 2 and comprises a high tension spark coil 55 connected by a cable 56 to the battery 2. A spark of one inch in length or longer is formed when the tip of the coil is held near the apparatus which is grounded. The slightest leak of propane will be ignited by the spark and thus may be detected. This new method is far superior to a torch test as there is no flame which may soil or otherwise injure the apparatus if there is no leak. Furthermore, it is relatively simple to supply every unit with such testing equipment.

Now that the principles of the invention have been outlined, the mechanical features illustrated in Figs. 4 to 8 which correspond to mechanical drawings of machines which have been actually built, will its described.

In keeping with the general trend towards a push button" operation and also in order to make the machine fool proof, a starting mechanism has been provided which takes care of all starting operations by the movement of a single lever 60, illustrated in Figs. 3, 4 and 6.

The starting mechanism not only effects the initiation of the automotive starter equipment which is conventional for combustion motors, but it also:

(a) Opens the solenoid 64 to release the compression of the compressor during the starting oi the motor I and only during this starting period;

(b) 0pens solenoid shut-off valve 35 and keeps it open only as long as the motor is running;

(0) Opens solenoid shut-off valve 32 in the fuel line and keeps it open only as long as the motor is running.

Fig. 6 illustrates the electric wiring scheme which effects these various functions. Pushing down the lever 60 to the position indicated in dotted lines in Fig. 4 results in:

(1) The closing of the circuit whereby the electric starter is operated by the battery;

(2) The operation of the double pole switch 59, thus effecting the closing of the circuit which actuates the unloading valve 64, the bottle feed valve 25 and the carburetor line valve 32, thereby opening these three solenoid valves.

After the motor I is running on propane, the lever 80 is released and by means of a spring pushed back into its original position, thereby opening the circuit of the electric starter and, by releasing'switch 59, opening the circuits of the solenoids 64, and 32. This closes the unloading valve 64. The other two solenoid valves 35 and 32, however, are kept open by the 'generator 3 by means of the relay 6!. This arrangement of tue relay involves a material advantage for the feed valve 35 and the carburetor line 32 will be closed the moment the generator and the motor I stop running.

Compared with standard closed refrigerating systems which require great care and expert knowledge in connection with their charging, removal of their refrigerant, and upkeep, this new system is relatively simple indeed, Even when this new machine is substantially completely filled with air, the machine is purged free of air in a very short time and the motor starts running on propane within thirty seconds. Within two minutes, the compressor has sucked out of the propane tank and compressed and condensed and passed into the receiver tank 20, enough liquid propane to reach the level of tube 24 at the sight glass 45. Cooling the bulb 26 by means of the propane spray leaving nozzle 25, results in the closing of the valve 29 in about ten seconds.

The gauge pressure at the suction side of the compressor will show approximately pounds as long as the storage tank is connected to the suction pipe I3 and this gauge pressure will drop to approximately 30 pounds, which is maintained by the constant pressure valve ll, after valve 29 is closed. The machine will then run under the full load of evaporator 9.

The theoretical principles of the transitory cycle and the fast cycle and. the mechanical constructions and controls associated therewith having been described in connection with the drawings, reference will now be made to the particular advantages of the construction illustrated in Fig. 3, Fig. 4 and Fig. 5. The, constructions illustrated in these drawings are of special value in mobile refrigerating jobs such as trucks and railway cars. In such constructions, the loading space, which is enclosed by the insulated walls of the truck or of the railway car, is most valuable as here the pay load is carried. Accordingly, I prefer to build a unit which utilizes the whole height of the loading space and therefore occupies but a minimum of floor space. The construction illustrated in Fig. 3, Fig. 4 and Fig. 5 has a height a of 65 inches, a width b of inches, and a length 0 of 44 inches. The unit is built as a packaged unit and does not require any particular installation work after being inserted into the body of the truck or of the railway car and connected by means of the flexible hose 39 with the propane storage tank.

The machine elements are mounted one on top of the other to obtain a minimum width b. A power take-off pulley-belt arrangement associated with the motor I drives shaft 4 and takes about one-third of its power to drive the rotor 5 of the condenser blower and the rotor 6 of the evaporator blower, which two rotors are mounted on the shaft 4. The condenser blower is equipped with a nozzle 51 and a diffuser 58 so that the air discharged from the condenser blower may serve to suck the air of! of the motor I from the engine compartment.

The unit is equipped with an L-shaped insulating wall 5| which is in alignment with the insulated wall of the loading space adjacent the unit compartment. All the machine elements are encased in a strong cage-like frame of angle irons, on top of which the bearings 62 and B3 for-the shaft 4 are mounted and to each side of which the condenser casing 3 and the evaporator casing 9 respectively are attached. In addition to utilizing but a minimum of floor space, this unit arrangement has the inherent advantages associated with a low level air intake and a high level air discharge for the evaporator blower. Further, this unit arrangement has the advantage inherent in the location of the exhaust hot air leaving the condenser and the engine compartment at the top. As the width b of the unit is a minimum, it is very accessible for repairs, belt adjustments and the like. In Fig. 3 the unit is shown in front elevation; in Fig. 5 the unit is illustrated as it appears from the top when installed in the front left corner of a truck or railway car. This construction provides for a convenient air intake to the condenser compartment and for easy access to the engine compartment. In other respects the unit is built in accordance with that shown in Fig. 1 and Fig. 2. A modified form of working unit is shown in Fig. '7 and Fig. 8. This modified unit has overall dimensions approximating that of a cube. The evaporator compartment E is separated from the condenser and engine compartment 0 by an insulated straight partition wall I. The unit is so arranged in relation to the cooling space that the compartnient E extends into the interior of the cooling space and the compartment 6 remains completely outside of the floor space occupied by the cooling space. The partition wall I is in the same plane as the wall W of the cooling space. A propane tank T is connected with the compartment C, and it too is arranged outside of the cooling space. This modified form of the unit is particularly practical when the same is to be inserted into existing walls of a space to be cooled, such as an insulated stone house, whereas the unit illustrated in Fig. 3, Fig. 4 and Fig. 5 would require an adaptation of the walls of the cooling space to the unit. However, the L-shaped insulating wall 5|, shown in Fig. 5, may in certain cases also be arranged to be in e same planes with existing rectilinear corner walls of a space to be cooled.

It is to be understood that other level control devices may be substituted to the level control de-' scribed which utilizes the thermal valve 29, without departing from the spirit of the invention and without deviating from the general principles of the transitory cycle and the fast cycle."

it will be obvious to those skilled in the art that various changes may be made in this device without departing from the spirit of the invention and therefore the invention is not limited to what is shown in the drawings and described in the specification but only as indicated-in the apv pended claims.

I claim:

1. The method of utilizing, in a compressorcondenser-expander refrigeration system, a mixture of hydrocarbons including components which are not condensible in the condenser of said system, said method comprising compressing said mixture in the compressor of said system, condensing the condensible components of the mixture in said condenser, evaporating said condensible components in the expander of said system and withdrawing the vapors from said expander by the compressor, while withdrawing vapors including said non-condensiblecomponents from the condenser, feeding the same as fuel to a motor, and withdrawing the mixture from a supply thereof and introducing into said system the withdrawn material, and limiting said withdrawal and introduction to such quantities per unit of time that the volume of non-condensible components introduced into the system is always smaller than the volume of fuel consumed by said motor in said unit of time.

2. The method of operating a refrigerating apparatus, comprising the steps of evaporating a re atively small amount of a volatile fuel in a cooling zone, withdrawing the resulting vapor from said zone, compressing said vapor, condensing said vapor to a liquid condition and collecting the same in a body and returning the fuel in liquid form from said body to the evaporating zone; withdrawing vapor from above the body of liquid and consuming the same as fuel; and introducing into said system fuel from a supply thereof to compensate for the amount withdrawn and controlling the rate of introduction by changes in the level of the liquid in said body.

3. The method as claimed in claim 2, wherein the fuel from said supply is introduced into the low-side of said system.

4. The method as claimed in claim 2, wherein the refrigerant is introduced into said refrigerating system in gas phase.

5. The method as claimed in claim 2, wherein the compressing of vapors withdrawn from said zone is alternated with the compressing of fuel from said supply.

6. The method as claimed in claim 2, wherein the vapor withdrawn from above the body of liquid is passed in heat exchange relation with compressed vapor prior to the condensation of said compressed vapor. V

7. The method of feeding a volatile medium to a consuming device from a storage receptacle; said methodcomprising withdrawing said medium from the latter; introducing the withdrawn medium in gaseous phase into a portion of a refrigerating circuit; mixing said medium with a stream of similar vapor moving through said circuit; compressing and condensing the mixture in a heat dissipating zone: diverting some of the mixture to said consuming device; collecting the liquefied medium; directing said medium into an evaporator zone; vaporizing such medium in said zone; withdrawing the resulting vapors from said zone and re-circulating them through the firstmentioned portion 'of said circuit and remixing them with freshly introduced vapors from said storage receptacle and regulating the rate of withdrawal of the medium from said storage receptacle by heat changes produced in one of said zones.

8. The method as claimed in claim 7, wherein the collected liquefied medium is directed into the evaporator zone in two different portions from two different levels of the collected liquid.

9. The method as claimed in claim 7, wherein control is exerted upon the two steps of diverting collectedliquefled medium into an evaporator zone and of introducing fresh medium from said storage receptacle to carry on these two steps alternately.

10. The method as claimed in claim 7, wherein control is exerted upon the two steps of withdrawing the medium from the storage receptacle and of introducing the withdrawn medium into the refrigerating circuit for the purpose of introducing the medium into the refrigerating circarbon as fuel to a fuel consuming device from a storage receptacle; said method comprising withdrawing fuel from said storage receptacle, introducing the withdrawn fuel as vapor into a portion of a refrigerating circuit, mixing such vapor with a stream of similar hydrocarbon vapor, compressing and condensing said mixture in a heat dissipating zone, diverting some of the mixture to said fuel consuming device, collecting the liquefied hydrocarbons, directing the collected hydrocarbons into an evaporating zone, vaporizing such hydrocarbons in said zone and re-circulating them through the first-mentioned portion of said circuit and there mixing them with freshly introduced hydrocarbon vapor from said storage receptacle and regulating the rate of withdrawal of the hydrocarbon from said storage receptacle by heat changes produced in one of said zones.

' PE'IEB SCHLUMBOHM. 

